U.S. patent application number 10/613104 was filed with the patent office on 2005-01-13 for methods and devices for creating bi-directional lsps.
Invention is credited to Chen, Feihong, Liu, Hua Autumn.
Application Number | 20050007960 10/613104 |
Document ID | / |
Family ID | 33564288 |
Filed Date | 2005-01-13 |
United States Patent
Application |
20050007960 |
Kind Code |
A1 |
Chen, Feihong ; et
al. |
January 13, 2005 |
Methods and devices for creating bi-directional LSPs
Abstract
Bi-directional Label Switched Paths (LSP) are created by
bundling a forward and backward LSP. The forward LSP is separately
generated from the backward LSP. The so-created, bi-directional LSP
can be deleted when delete path requests are generated and received
by both the forward and backward LSPs, respectively.
Inventors: |
Chen, Feihong; (Lowell,
MA) ; Liu, Hua Autumn; (Holmdel, NJ) |
Correspondence
Address: |
HARNESS, DICKEY & PIERCE, P.L.C.
P.O. Box 8910
Reston
VA
20195
US
|
Family ID: |
33564288 |
Appl. No.: |
10/613104 |
Filed: |
July 7, 2003 |
Current U.S.
Class: |
370/249 ;
370/250 |
Current CPC
Class: |
H04L 45/00 20130101;
H04L 45/245 20130101; Y02D 30/50 20200801; Y02D 50/30 20180101;
H04L 45/50 20130101 |
Class at
Publication: |
370/249 ;
370/250 |
International
Class: |
H04L 012/26 |
Claims
We Claim:
1. A network device operable to: generate and send a backward path
request message to a source of a separately generated, initial
forward path request message associated with a forward Label
Switched Path (LSP) between the device and the source; and receive
a backward path reservation message from the source in order to
establish a backward LSP between the device and the source, wherein
the separately generated forward and backward LSPs form a
bi-directional LSP between the device and the source.
2. The device as in claim 1 further operable to generate and send
an initial, forward path reservation message to the source in order
to establish the forward LSP after receiving the initial forward
path request message.
3. The device as in claim 1 further operable to generate and send a
backward path reservation message to a destination after receiving
a backward path request message from the destination in order to
establish a backward LSP between the device and the
destination.
4. The device as in claim 3 further operable to separately generate
and send a forward path request message to the destination in order
to establish a forward LSP between the device and the destination,
wherein the separately generated forward and backward LSPs between
the device and the destination form a bi-directional LSP between
the device and the destination.
5. The device as in claim 1 wherein the forward and backward LSPs
between the device and source comprise the same path.
6. The device as in claim 4 wherein the forward and backward LSPs
between the device and destination comprise the same path.
7. The device as in claim 1 further operable to generate the
backward path request message based on backward path parameters
contained in the initial forward path request message.
8. The device as in claim 7 further operable to generate the
backward path request message based on routing information
contained within the parameters.
9. The device as in claim 7 further operable to query a local
database to obtain routing information in order to generate the
backward path request message when routing information is not
contained within the parameters.
10. The device as in claim 7 further operable to generate the
backward path request message based on a quality-of-service (QoS)
indicator contained within the parameters.
11. The device as in claim 7 further operable to generate the
backward path request message based on best effort routing
information when a QoS indicator is not contained within the
parameters.
12. The device as in claim 7 wherein the traffic parameters
comprise parameters selected from the group consisting of a
bi-directional LSP indicator, QoS indicator and routing
information.
13. The device as in claim 1 further operable to request backward
traffic parameters from the source when the initial path request
message does not contain such parameters.
14. The device as in claim 1 further operable to generate and send
a first delete path message to the source and to receive a second
delete path message from the source in order to delete the
bi-directional LSP.
15. The device as in claim 14 further operable to send the first
delete path message to the source before receiving the second
delete path message from the source.
16. The device as in claim 14 further operable to send the first
delete path message to the source after receiving the second delete
path message from the source.
17. A network device operable to generate and send a backward path
reservation message to a destination after receiving a backward
path request message from the destination in order to establish a
backward LSP between the device and the destination.
18. The device as in claim 17 further operable to separately
generate and send a forward path request message to the destination
in order to establish a forward LSP between the device and the
destination, wherein the separately generated forward and backward
LSPs between the device and the destination form a bi-directional
LSP between the device and the destination.
19. The device as in claim 18 wherein the forward and backward LSPs
between the device and destination comprise the same path.
20. The device as in claim 17 further operable to generate and send
a first delete path message to the destination and to receive a
second delete path message from the destination in order to delete
the bi-directional LSP.
21. The device as in claim 20 further operable to send the first
delete path message to the destination before receiving the second
delete path message from the destination.
22. The device as in claim 20 further operable to send the first
delete path message to the destination after receiving the second
delete path message from the destination.
23. A method for creating a bi-directional LSP comprising the steps
of: generating and sending a backward path request message to a
source of a separately generated, initial forward path request
message associated with a forward Label Switched Path (LSP) between
the device and the source; and receiving a backward path
reservation message from the source in order to establish a
backward LSP between the device and the source, wherein the
separately generated forward and backward LSPs form a
bi-directional LSP between the device and the source.
24. The method as in claim 23 further comprising the steps of
generating and sending an initial, forward path reservation message
to the source in order to establish the forward LSP after receiving
the initial forward path request message.
25. The method as in claim 23 further comprising the steps of
generating and sending a backward path reservation message to a
destination after receiving a backward path request message from
the destination in order to establish a backward LSP between the
device and the destination.
26. The method as in claim 25 further comprising the steps of
separately generating and sending a forward path request message to
the destination in order to establish a forward LSP between the
device and the destination, wherein the separately generated
forward and backward LSPs between the device and the destination
form a bi-directional LSP between the device and the
destination.
27. The method as in claim 23 wherein the forward and backward LSPs
between the device and source comprise the same path.
28. The method as in claim 26 wherein the forward and backward LSPs
between the device and destination comprise the same path.
29. The method as in claim 23 further comprising the step of
generating the backward path request message based on backward path
parameters contained in the initial forward path request
message.
30. The method as in claim 29 further comprising the step of
generating the backward path request message based on routing
information contained within the parameters.
31. The method as in claim 29 further comprising the step of
querying a local database to obtain routing information in order to
generate the backward path request message when routing information
is not contained within the parameters.
32. The method as in claim 29 further comprising the step of
generating the backward path request message based on a
quality-of-service (QoS) indicator contained within the
parameters.
33. The method as in claim 29 further comprising the step of
generating the backward path request message based on best effort
routing information when a QoS indicator is not contained within
the parameters.
34. The method as in claim 29 wherein the traffic parameters
comprise parameters selected from the group consisting of a
bi-directional LSP indicator, QoS indicator and routing
information.
35. The method as in claim 23 further comprising the step of
requesting backward traffic parameters from the source when the
initial path request message does not contain such parameters.
36. The method as in claim 23 further comprising the steps of
generating and sending a first delete path message to the source
and receiving a second delete path message from the source in order
to delete the bi-directional LSP.
37. The method as in claim 36 further comprising the step of
sending the first delete path message to the source before
receiving the second delete path message from the source.
38. The method as in claim 36 further comprising the step of
sending the first delete path message to the source after receiving
the second delete path message from the source.
39. A method for creating a bi-directional LSP comprising the steps
of generating and sending a backward path reservation message to a
destination after receiving a backward path request message from
the destination in order to establish a backward LSP between the
device and the destination.
40. The method as in claim 39 further comprising the steps of
separately generating and sending a forward path request message to
the destination in order to establish a forward LSP between the
device and the destination, wherein the separately generated
forward and backward LSPs between the device and the destination
form a bi-directional LSP between the device and the
destination.
41. The method as in claim 40 wherein the forward and backward LSPs
between the device and destination comprise the same path.
42. The method as in claim 39 further comprises the steps of
generating and sending a first delete path message to the
destination and to receive a second delete path message from the
destination in order to delete the bi-directional LSP.
43. The method as in claim 42 further comprising the step of
sending the first delete path message to the destination before
receiving the second delete path message from the destination.
44. The method as in claim 42 further comprising the step of
sending the first delete path message to the destination after
receiving the second delete path message from the destination.
45. A network device comprising: means for generating and sending a
backward path request message to a source of a separately
generated, initial forward path request message associated with a
forward Label Switched Path (LSP) between the device and the
source; and means for receiving a backward path reservation message
from the source in order to establish a backward LSP between the
device and the source, wherein the separately generated forward and
backward LSPs form a bi-directional LSP between the device and the
source.
46. The device as in claim 45 further comprising means for
generating and sending an initial, forward path reservation message
to the source in order to establish the forward LSP after receiving
the initial forward path request message.
47. The device as in claim 45 further comprising means for
generating and sending a backward path reservation message to a
destination after receiving a backward path request message from
the destination in order to establish a backward LSP between the
device and the destination.
48. The device as in claim 47 further comprising means for
separately generating and sending a forward path request message to
the destination in order to establish a forward LSP between the
device and the destination, wherein the separately generated
forward and backward LSPs between the device and the destination
form a bi-directional LSP between the device and the
destination.
49. The device as in claim 45 wherein the forward and backward LSPs
between the device and source comprise the same path.
50. The device as in claim 45 wherein the forward and backward LSPs
between the device and destination comprise the same path.
51. The device as in claim 45 further comprising means for
generating the backward path request message based on backward path
parameters contained in the initial forward path request
message.
52. The device as in claim 51 further comprising means for
generating the backward path request message based on routing
information contained within the parameters.
53. The device as in claim 51 further comprising means for querying
a local database to obtain routing information in order to generate
the backward path request message when routing information is not
contained within the parameters.
54. The device as in claim 51 further comprising means for
generating the backward path request message based on a
quality-of-service (QoS) indicator contained within the
parameters.
55. A network device comprising means for generating and sending a
backward path reservation message to a destination after receiving
a backward path request message from the destination in order to
establish a backward LSP between the device and the
destination.
56. The device as in claim 55 further comprising means for
separately generating and sending a forward path request message to
the destination in order to establish a forward LSP between the
device and the destination, wherein the separately generated
forward and backward LSPs between the device and the destination
form a bi-directional LSP between the device and the destination.
Description
BACKGROUND OF THE INVENTION
[0001] Multi-Protocol Label Switched (MPLS) networks transfer
packets of information using virtual connections referred to as
"Label Switched Paths" (LSPs). There exists techniques for creating
LSPs within an MPLS network. As is known by those of ordinary skill
in the art, MPLS standards necessitate that each LSP operate in a
unidirectional manner (e.g., forwards or backwards). There exists a
newer standard named Generic MPLS ("GMPLS") which sets forth
techniques for creating LSPs in both directions, so-called
"bi-directional" LSPs. GMPLS techniques have their drawbacks,
however. GMPLS techniques are not compatible with MPLS-based
devices because, for example, in GMPLS LSPs for both the forward
and backward directions are set up simultaneously using a single
request message or the like. In contrast, MPLS-based devices can
only create a single LSP in one direction at a time. The inability
of MPLS-based devices to set up LSPS in both directions
simultaneously prevents them from using GMPLS techniques.
SUMMARY OF THE INVENTION
[0002] Bi-directional LSPs can be created, in accordance with the
principles of the present invention, by bundling separately created
LSPs. Bundling is carried out by creating an LSP in one direction
(e.g., forward path) and then creating a separately generated LSP
in the opposite direction. The LSP generated in the opposite
direction is referred to as a backward path.
[0003] In accordance with one embodiment of the invention, a
network device is operable to generate and send a backward path
request message to a source of a separately generated, initial
forward path request message. After sending the backward path
request message, the device awaits the receipt of a backward path
reservation message from the source. Upon receiving this
reservation message, an LSP in the opposite or backward direction
is established. Having separately generated and established both a
forward and backward LSP, the two LSPs will act as a bi-directional
LSP between the device and the source.
[0004] In the embodiments just explained, the network device was
operating as a destination device. In additional embodiments of the
present invention, the network device may act as a source
device.
[0005] In yet further embodiments of the present invention,
backward path parameters (e.g., bi-directional LSP indicator,
quality-of-service (QoS) indicator, routing information, etc.)
contained in an initial, forward path request message may be used
to generate a backward LSP.
BRIEF DESCRIPTION OF THE DRAWINGS
[0006] FIG. 1A depicts a number of network devices within a
simplified MPLS network.
[0007] FIG. 1B depicts the creation of a bi-directional LSP between
a source device and a network device in accordance with one
embodiment of the present invention.
[0008] FIG. 1C depicts the creation of a bi-directional LSP between
a destination device and a network device according to another
embodiment of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0009] Referring to FIG. 1A, there is shown an MPLS network 100
which comprises a plurality of MPLS devices 1-3 (e.g., routers,
switches, etc.). Devices 1-3 comprise either a source or
destination device. In some cases, each device 1-3 may operate as
both a source and destination device. It should be understood that,
though only 3 devices are shown in FIG. 1A, an MPLS network may
contain any number of devices. That is to say, MPLS network 100
typically comprises a number of intermediate devices (not shown)
between devices 1 and 2 and between devices 1 and 3, respectively.
Because their presence is not necessary for an understanding of the
present invention, the intermediate devices have been omitted from
FIGS. 1A-1C. At some point in time it becomes necessary to create
one or more bi-directional LSPs within network 100 using at least
devices 1-3.
[0010] Referring to FIG. 1B, there is shown a bi-directional LSP,
denoted BLSP.sub.1, between network device 2 operating as a source
device and network device 1 operating as a destination device.
Though referred to in the singular, it should be understood that
the bi-directional BLSP1 actually comprises two separate LSPs; a
forward LSP 21 and a backward LSP 12. Though the network device 2
is operating as a source device and the network device 1 is
operating as a destination device in FIG. 1B, it should again be
understood that each of these devices may operate as a source,
destination or source and destination device. Network devices 1 and
2 have been so designated as destination and source devices,
respectively, only for the purpose of making the explanation of
features of the present invention easier to understand.
[0011] In one embodiment of the present invention, bi-directional
BLSP.sub.1 is created as follows. Source device 2 is operable to
generate and send an initial, forward path request message, a, to
network device 1 in order to initiate the establishment of a
forward LSP. Upon receiving this path request message, device 1 is
operable to generate and send a forward path reservation message,
b, to the source device 2 (sometimes referred to as just "source").
In this manner, a forward LSP is created between the source 2 and
network device 1.
[0012] In one embodiment of the present invention, the initial,
forward path request message also contains "backward path
parameters". These parameters are used by the device 1 to initiate
the creation of a backward LSP. In one embodiment of the present
invention, the network device 1 uses the backward path parameters
to generate and send a backward path request message, c, to the
source device 2. This request message is separately generated from
the forward path request message prepared by the source device 2.
It can be said then, that the forward and backward LSPs are
generated using separately generated forward and backward path
request messages. This separate generation of request messages
leads to the separate generation of a forward and backward LSP all
of which may be carried out by MPLS-based devices. Continuing, upon
reception of a backward path reservation message, d, by device 1 a
backward LSP is created.
[0013] In the discussion above it was mentioned that backward path
parameters contained within the initial forward path request
message a are used to initiate the steps necessary to create a
backward LSP. How this occurs is worthy of some additional
discussion. The backward path parameters may comprise one or more
of the following: a bi-directional LSP indicator, a QoS indicator
and/or routing information. The presence of the bi-directional LSP
indicator informs a destination device that such an LSP needs to be
set up, triggering the destination device to generate a backward
path request message or the like.
[0014] Though this indicator must always be present within the
parameters to initiate the creation of a bi-directional LSP, the
parameters may not always contain QoS indicators or routing
information.
[0015] When a request message contains routing information within
the path parameters, the receiving device (e.g., destination
device) must use this routing information to set up a backward LSP.
When, however, no routing information is contained within the path
parameters, the destination device is operable to query a local
database associated with the device to obtain routing
information.
[0016] The information selected by the destination device from
within the database is affected by the presence or absence of a QoS
indicator within the path parameters. For example, if such an
indicator is sent within the parameters, then the destination
device is operable to select routing information which meets the
same QoS ( e.g., selects nodes which offer the same QoS to be a
part of the backward LSP). If, however, no QoS indicator is present
within the path parameters, then the destination device is further
operable to select routing information which corresponds to a "best
efforts" route (e.g., nodes which provide some minimum or average
QoS).
[0017] At some point in time after the bi-directional BLSP, is
created, there may come a time when it is necessary to terminate or
otherwise delete this bi-directional LSP. In yet further
embodiments of the invention, both devices 1 and 2 are operable to
generate delete path messages in order to delete the bi-directional
LSP.
[0018] More specifically, device 1 is operable to generate and send
a first delete path message to the source device 2 and to receive a
second delete path message from the source device 2 in order to
delete the bi-directional LSP.sub.1. It should be understood that
the order in which the delete path messages are sent or received is
not important to the deletion of the bi-directional LSP. That is to
say, the first delete path message generated by the network device
1 may be sent to the source 2 before or after the network device 1
receives the second delete path message from the source device 2.
In addition, the generation of the second message may not be
triggered by the reception of the first message. The designations
"first" and "second" are not meant to imply a chronological order
necessarily. Instead, these designations are used only to point out
that two separate messages need to be sent before a bi-directional
LSP is deleted.
[0019] As indicated initially above, the network device 1 is
operating as a destination device located at a destination node or
the like. Alternatively, device 1 can also operate as a source
device. In a further embodiment of the present invention, when the
device 1 operates as a source device it may be operable to initiate
the creation of a bi-directional LSP in between itself and device 3
which is operating as a destination device. Referring to FIG. 1C,
there is shown a bi-directional LSP, BLSP.sub.2 , in between device
1 and destination device 3. To avoid being repetitious, but to make
the example shown in FIG. 1C more understandable, only backward LSP
31 of bi-directional BLSP.sub.2 is shown. It should be understood,
however, that BLSP.sub.2 also comprises a bundled, forward LSP.
[0020] BLSP.sub.2 may be created as follows. Device 1 is operable
to separately generate and send a backward path reservation
message, f; to the destination device 3 after receiving a backward
path request message, e, from the destination device 3. Once the
destination device 3 receives the backward path reservation
message, backward LSP 31 is created between the device 1 and
destination device 3. It should be understood that the device 1 has
separately generated and sent a forward path request message, e, to
the destination device 3 in order to establish the forward LSP (not
shown) between the device 1 and destination device 3. As before,
these separately generated forward and backward LSPs form a
bi-directional LSP, BLSP.sub.2, between device 1 and destination
device 3. Similar to the bi-directional LSP shown in FIG. 1B, the
bi-directional BLSP.sub.2 may be deleted when both devices 1 and 3
generate and send delete path messages to one another. It should be
understood that the delete path messages sent by both devices 1 and
3 may be sent in any order provided the order results in the
deletion of the bi-directional BLSP.sub.2.
[0021] In an alternative embodiment of the invention, the forward
and backward LSPs which comprise the bi-directional BLSP.sub.2 may
in fact comprise the same path. In yet another embodiment, the
backward path may be created first, followed by the forward
path.
[0022] The above discussion has set forth some examples of the
ideas envisioned by the present invention. Practically speaking, it
is impossible to set forth each and every example. Variations of
the examples given above are considered to be within the spirit and
scope of the present invention, the scope of which is more aptly
defined by the claims which follow.
* * * * *